Electric furnace



' June 23,1943. o. JUNKER Em 2,323,031

ELECTRIC FURNACE Filed Oct. 28, 1949 4 Sheets-Sheet 1 .Zrn/emo/"s` Orro duNKER ERICH BREUER M KARL. `KMA UFF WW1. ArrYS.

June 29, 1943.

o. JuNKl-:R ETAL ELECTRIC FURNACE Filed Oct. `2a, 1940 4 sheets-sheet 2 Inventors OTTO' JUNKER .ERICH BREUER KARL KNAUFF W. ATTYS.

v o. JUNKER ET AL 2,323,051

ELECTRIC FURNACE Filed oct. 28, 1940 4 sheets-sheet s Inv OTTO JUNKE ERlcH BR KARL KN mm l l.

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June 29, 1943.

June 29, 1943. Q JUNKR ETAL, 2,323,051

ELECTRIC FURNACE Fiied oct. 28, 1940 4 sheets-sheet 4 Imnv? OTTO dUNKER ERlH BREUER KARL KNAUFF Patented June 29, 1943 ,l "j UNITED Otto Junker, Lammeradorf, ber Aachen, Erich Breuer. Strauch. Kreis Monschau, and Karl jinauil, Lammersdorf, iiber Aachen, Germany:

vested in the Alien Property Custodian Application October 28. 1940; Serial No. 363,202

In Germany'M'ay 20, 1938 The invention relates to an electric furnace. 'for ,instance to a revolving melting furnace. Electric furnaces are known which are, equipped with at least one electrical resistance heating rod. of carbon, graphiteor the like, the heating rod being supported at one side by a cooled metal terminal which in turn is arranged in a bearing provided on the outside of the furnace wall and so that,`after detaching the current feedingl device, the heating rod can be pulled out of the furnace in axial direction together with the metal terminal. As a rule both ends of the heating rod, y

in such furnaces, are equippedl with cooled metal terminals, so that a corresponding bearing is provided on each side for the metal terminal. The cooling can be effected by a gaseous or liquid medium. The current feeding device was heretoforeconnected to the extreme end of the terminal which projected from the furnace this resulting in a long current path to the heating rod, and requiring separate and complicated bearings for the current supply device connected to the terminal and for guiding the same. At

`the same time the metallic packing of the terminal at itsvpassage through the furnace wall caused difficulties, because the packing rings are apt to jam in their guides. The jamming of the-- which contact faces on the terminal and car.

riage can be detachably tightened, and the contact-carriage is mounted in stationary upright bearings with limited capacity for movement inv the direction axial to the heating rod, for the purpose of accommodating expansion and contraction due to' heat.

These upright bearings may be arranged on the furnace wall or at the side of thefurnace. 'Ihe contact faces between the contact carriage and the tubular terminal can in this manner be brought very close to the furnace wall, so that the current supply path becomes comparatively short. The contact carriage provides a secure support and accurate guide for the terminal tube, so that this tube can be pulled out from the furnace or inserted into the same together with the heating rod and without disturbing turning or rocking movement. The accurate axial guiding of the contact carriage in the upright bearingv prevents transverse shifting of the heating rod during its insertion or removal and at the same time a certain axial movability of the terminal is made possible to accommodate expansion and contraction of the heating rod due to temperaturel changes which is especia1Lv.necessary in furnaces, in which the heating rod is clamped at both ends in metal terminals. For

this purpose preferably one of the contact carriages is fixed and the other one is shiftable against spring pressure or the like, in order to allow variations in length of the heating rod during service.

In a further development of the invention, the part of thecontact carriage between the upright bearing and the terminal tube forming the contact face is constructed as a hollow cone tapering towards the furnace, against which cone the correspondingly conical part of the terminal tube is pressed by means of va clampingr device pro- `vided on the contact carriage. Besides the accurate centering of the terminal tube by the contact faces of the contact carriage a comparatively large contact area is obtained. The conical form of the contact vface makes it possible to obtain, owing to the wedge effect, a high contact pres# sure and therewith a perfect conductivity foi the electric current across the contact area this being of great value for the high current density at said area.

The connection between the tubular metal terminal and the heating rod or rods of resistance material may be carried out in various manner. The terminal tube preferably has an axial recess of slight conicity engaging a correspondingly coned end of the heating rod whereby frictonal coupling of the rod and tube results. If it is desirable to give the terminal tubes a similar shape at both sides of the furnace, an intermediate piece must be employed, in order to make possible the axial pulling out, which intermediate piece is adapted to be inserted into the conical recess of the terminal tube and is of material similar to that of the heating rod is arranged on the side of the furnace' remote Y from the side at which the heating rod is pulled out. The intermediate piece on its end facing the interior'of the furnace, has a cavity adapted to receive the end of the heating rod, said cavity having its bearing faces spherical, or strongly inclined to the central axis.

An especially favorable connection for the contact tube and the heating rod is obtained by interposing between these elements a coupling member arranged in the furnace Wall which" member is connected to the metal termlnal by a pin and receives the end of the heating rod. This coupling member must consist of a material possessing similar prop-l erties as the heating rod itself, for instance' a distance that its life is' considerably lengthened. A further advantage of the insertionof this coupling member consists in that the sensitive connection with the metal terminal can be established outside whereas especial attention to the contact between heating rod and coupling member is not required owing to the comparative insensitiveness of thisV contact.

As this coupling member has to sustain only a little portion of the total heat, its diameter need not be greater or not much `greater than that of the metallic terminal tube, so that the made necessary owing to the'terminal contacts. 20

When heating rods are employed which are made of soft materials such as carbon or graphite it is advisable to give to the cooled metal contact tube at the terminal point such little thickness that softening of the metal under the influence of the furnace temperature is avoided in order to avoid premature destruction of the metal terminal.

Several embodiments of the invention are illustrated by way f example in the accompanying drawings, in which Fig. 1 shows in longitudinal section a furnace with one or several heating rods, the bearing for the metal terminal in the left hand half of the furnace being arranged on the furnace wall, in the right hand half, however, separate from the furnace wall.

Fig. 2 is a longitudinal section through a iurnace wall and amounting of a contact,

Fig. 3 is a section on line III- III of Fig. 2,

Fig. 4 is a horizontal longitudinal section through the mounting of a. contact,

Fig. 5 is a section on line V-V of Fig. 4,

Figs. 6 and '7 show the construction and arrangement of a rolling packing between terminal tube and furnace wall,

Fig.. 8 shows in longitudinal section another form of construction with employment of special coupling pieces,

Fig. 9 shows in longitudinal section another form of construction of a heating rod with the metal terminal pieces,

Fig. 10 shows in longitudinal section another form of construction of the coupling piece,

Fig. 11 is a cross-section through a furnace comprising three heating rods arranged the one at the side of the other.

In the electric furnace i shown in Fig. i, theheating rod 2 is mounted at both ends, with interposition of coupling pieces 3 consisting of carbon or graphite or the like, between metal terminals 4 which, through a current feed body B, are arranged rigidly, or yieldably under spring pressure, in bearings 5 fixed on the furnace wall or erected at the side of the furnace. The heating rod` is connected by a tenon at one end with the metal contact so that it can be axially pulled out with the same from the furnace after detaching from the current supply body 6. Evidently the current feed and mounting may be provided only 'on one furnace side .when a suitable connection is selected.

The coupling piece '3 consists of a material having similar properties as the heating rod 2 itself. The diameter of the coupling P1 it not greater or .not essentially greater than that of the metallic terminal or contact'tube l (Fig. 2), but the cross-section is substantially great- `er than that of the heating rod 2.

In the form of construction shown in Figs. l and 2, the coupling piece is constructed like a sleeve. On the side of the furnace at which the pulling out takes place, see Fig. 1 at vthe left and Fig. 2, the sleeve has two oppositely directed slightly-conical cavities 3a, Ib, one adapted to receive the end of the heating rod. and the other, a conical hollow pin 1a, which forms an extension of the contact tube 1. As can be seen from Fig. 2, only the hollow pin la and the end face 1b of the contact tube 1, said end -face facing the coupling piece, are made oi' heat-proof material and connected by welding at 'lc with the remaining portion of the contact tube 1 consisting of iron or the like.n

On the other side of the furnace, as shown at the right hand side of Fig. l, a coupling sleeve is shown which has only on the outer side a slightly conical bore 3b for the conical pin 1a ci the contact tube 1, whereas this sleeve has a spherical or steeply conical indentation 3c, against which the heating rod is elastically pressed as hereinafter described.

The contact tube 1 is slidably guided on the outer side of the furnace wall in a carriage l. The contact carriage and the contact tube have conical contact faces 9 tapering towards the furnace. With the aid of a clamping bow lll mounted on the end of the contact carriage, engaging over the end of the contact tube, the contact faces 9 of contact tube and contact carriage are pressed the one against the other, and the contact tube is thus solidly clamped in the contact carriage. 'I'his clamping bow is pivoted to the under side of the carriage 8 and opposite the pivot has a bore traversed by a bolt Ib which is pivoted to the carriage 8 at a point above the pivot of the bow. The threads of the bolt engage corresponding screw threads in the boss of a handwheel iilc and by suitably turning said wheel the curved surface of the bow presses against a complementary surface on an extension 1g of the contact tube 1. After detaching the handwheel, turning down the clamping bow l0, and lifting off the connections for the cooling water to the metal Contact tube 1, the contact tube 1, and with the same the heating rod 2, can be pulled out of the furnace. The separation of the contact faces il rigidly clamped the one with the other and therewith the pulling out ci the contact tube from thev carriage 8 is preferably initiated by a cam lila on the bow iD which, when the bow ill is turned down, is pressed l against the end face if of a slot in the extension of the Contact tube. The contact carriage, to which the current .feed wires il are connected, is guided by means of slide bearings such as ballor roller-bearings i2 so that it can be axially shifted in the uprightbearings i3, as shown in Figs. 3 to 5. The carriage may be secured in the upright bearings i3. The carriage sliding movement to the right (Fig. 2) is resisted by springs i4 or the like which are interposed between extensions I5 of the carriage B and the fixed upright bearings I3. The carriage can thus yield or follow by shifting in its guide when the length of the contact is altered, and the springs i5 produce elastic pressure on the rod 2. The accurate axial shiftable mounting of the contact carriage enables at any time the introduction and pulling out of the contact tube and heating rod free from disturbance. The feed and discharge pipes Il for the cooling medium to the contact tube 1, as clearly shown in Figs. 2 and 3, arev fixed in a bridge I1 which is supported relatively to the carriage 8 by springs Il. Through the contact tube 1 a supply pipe Ita for cooling water extends.'

On the lower side of thebridge an elastic gasket I9 is provided.' 'Ihe bridge is pressed against the contact tube in opposition to the action of springs I8 by means of an eccentric 28 mounted on the contact carriage. By releasing the eccentric, the bridge I1 is automatically lifted off the contact tube by the action of the springs. As clearly shown in the drawings, any connecting sockets or cams on the outeiside'of the contact ed to be pushed into a cylindrical chamber 24 mounted on the furnace wall or provided in this wall, an annular space being left free in this chamber. On the neck extension, at least one hollow or solid ring 25 of elastic material such as rubber is arranged which rolls on the cylindrical faces of neck-extension and chamber 24 of the furnace wall and is compressed between them, so that, when the neck-extension is inserted into the ring-shaped chamber, no appreciable resistance to movement occurs, which is a special advantage for the contact carriage shiftably mounted in opposition to spring force. The rubber ring or the rubber rings not-only form a packing, but also a good isolation between contact tube and furnace wall. The bore of the contact carriage is conically widened towards the furnace to form a baille surface 2l for the heat radiated from the furnace through the annular gap 28, as shown in Fig. 6, from which the heat rays are deflected to the cooled contact tube 1. Another radiation protection for the packing ring is formed by a collar 28, which at the same time serves as a stop of the rolling path for the ring 25. As shown in the upper half of Fig. 6, the outer rolling path for the packing ring 25 may be formed by a simple angular profile. It is, however, rnore practical if both rolling paths for the packing ring 25 are surrounded, as shown in' the lower half of Fig. 6 or of Fig. 2, by chambers to which cooling medium is admitted. As flowing out of hot air from the furnace is prevented by the packing, a permanently cooled air bolster is formed in front of the packing and protects the same against rapid destruction. As shown in Fig. '7, the rolling packing ring may be arranged directly on the contact tube 'l and conducted towards cylindrical faces of a correspondingly dimensioned bore of the furnacewall or of an extension of the furnace wall, preferably surrounded by cooling chambers. At the same time rolling rings may be provided on the contact tube asaaosr f 3 together' with the packing rings by axial shifting of the contact carriage, so that the packing rings can be easily examined or exchanged. The easy and complete separation of contact carriage and packing from the furnace wall is especially ma'- terial for furnaces in which the mounting ofthe contact is independent to that ofthe furnace.

Fig. 8 shows a form of construction with a slightly modified construction of thecoupling pieces 3. T he coupling pieces 3 are equipped with cylindrical bores 3d and 3e for the connection with corresponding screw-threaded pins 1d of the contact tube 1. On the side from which the pulling out is done, i. e. the left side in Fis. 8, the end of the heating rod 2, similar as in Figs. l and 2, is pushed into a slightly conical cavity 3a of the coupling sleeve 3. On the other side of the furnace the coupling sleeve 3 has a spherical cavity 3c as in'Flg. 1 for holding the right hand end of the heating rod. When the contact tube 4 1 is pulled out towards the left side the heating rod 2 is carried along.

The screw-threaded bores 3d and 3e may evidently also be conical. At a screw connection between coupling piece 3 and metal terminal- 1 at least one of the end faces 1e of the pin 1d is made to press against the coupling piece, besides the outer wall of the connection, for enlarging the total contact surface according to Fig. 8.

Fig, 9 showsan embodiment of the invention,

in which the coupling lpieces 3 are omitted. Ori,l

the side on which the pulling out is done the conical end of the heating rod is inserted into a conical recess 1g of the contact tube 1 said recess having slightly inclined walls. On the other l side of Fig. 9'(left hand side) a contact tube of as well as on the neck-extension of the contact similar construction is provided. In order to permit axial pulling out of the heating rod together with the right hand contact tube 1,an intermediate piece 29 is inserted, in this construc- -tion between the end of the heating rod and the In the embodiment illustrated in Fig. l0 the holding means for the heating rod on the side remote from the side at which the pulling out is done diners essentially from that shown in Fig. 9 in that the intermediate Apiece 29a similar to the coupling pieces 3 of the Figs. 1, 2 and 8, has a considerably larger cross-section than the heating rod and is inserted in the conical chamber of the contact tube 'l by a slightly conical pin 29h.

Fig. 11 shows in cross-section a furnace accoding to the invention with three juxtaposed ro s.

Theinventive idea is applicable in all kinds of electric furnaces and heating arrangements with heating rods of resistance material such as for instance rotary smelting furnaces and hearth smelting furnaces.

We claim:

1. An electric furnace comprising a resistance heating rod, awater-cooled metal terminal connected to said rod at one end of the latter, a carriage disposed outside the furnace, current feed wires connected to saidcarriage, means on said carriage for detachably clamping said terminal in the carriage, and a stationary support in which said carriage is mounted with capacity yfor limitedf'movement relatively to the furnace in a direction axial to the heating rod,

saidcarriage having a conical bore surrounding and engaging a corresponding lconical surface in which and carriage u mounted with capacity for limited movement relatively to the furnace in a direction axial to the heating rod, said carriage having a cylindrical extension axially slidable in a bearing in said stationary support.

3. An electric furnace comprising a resistance heating rod, a water-cooled metalterminal connected to saidrod at one end of the latter, a

' carriage disposed outside the furnace, current feed wires connected to said carriage, means on said carriage for detachably clamping said terminal in the carriage, a stationary support in which said carriage is mounted with capacity for limited movement relatively to the furnace in a direction axial to the heating rod, a conduit for admission of cooling medium to the interior of the terminal, a conduit for discharge of cooling medium from said terminal, a bridge having elastic packing means and extending over the ends of said conduits and having parts therein communicating with said conduits, flexible hose connections attached to said bridge, and means for pressing the bridge against the terminal.

4. An electric furnace comprising a resistance heating rod, a water-cooled metal terminal connected to said rod at one end of the latter, a carriage disposed outside the furnace, current feed wires connected to said carriage, means on said carriage for detachably clamping said terminal in the carriagel a stationary support -in which said carriage is mounted with capacity for limited movement relatively to the furnace in a direction axial to the heating rod,- the carriage having an annular extension at the end adjacent the furnace and surrounding the terminal, and the opposing wall of the furnace having a cylindrical chamber receiving said extension, and at least one packing ring of elastic material interposed between the furnace wall and said extension.

5. An electric furnace comprising a resistance heating rod, a water-cooled metal terminal connected to said rod at one end of the latter, a carriage disposed outside the furnace, current feed wires connected to said carriage, means on said carriage for detachablyclamping said terminal in the carriage, a stationary support in which said carriage is mounted with capacity for limited movement relatively to the furnace in a direction axial to the heating rod, the carriage having an annular extension at the end adjacent the furnace and surrounding the terminal, and the opposing wall of the furnace having a cylindrical chamber receiving said extension, and at least one packing ring of elastic material interposed between the furnace wall and said extension,` said packing ring being of circular crosssection adapted to roll under pressure.

6. An electric furnace comprising a resistance heating rod, a water-cooled metal terminal connected to said rod at one end of the latter, a carriage disposed outside the furnace, current feed wires connected to said carriage, means onl said carriage :cr dctachably clamping said tcrminal in the carriage, a stationary support in which said carriage is mounted with capacity for limited movement relatively to the furnace in a direction axial to the heating rod, and a coupling piece is interposed between the resistance heating rod and the terminal and connected to the latter, said piece consisting of a material possessing similar properties to the heating rod, its diameter corresponding approximately to that of the terminal, and its cross-section faces and its faces of contact with the rod and terminal being of `greater dimensions than the cross-section of the heating rod, said coupling piece being connected with an end oi' the heating rod by a pin in such a manner that when the corresponding terminal is axially pulled out of the furnace said heating rod is also withdrawn.

7. An electric furnace comprising a resistance heating rod, a water-cooled metal terminal connected to said rod at one end of the latter, a carriage disposed outside the furnace, current feed wires connected to said carriage, means on said carriage for detachably clamping said terminal in the carriage, a stationary support in which said carriage is mounted with capacity for limited movement relatively to the furnace in a direction axial to the heating rod, and a coupling piece interposed between the resistance heating rod and the terminal and connected to the latter, said piece consisting of a material possessing similar properties to the heating rod, its diameter corresponding approximately to that of the terminal, and its cross-section faces and its faces of contact with the rod and terminal being of greater dimensions than the cross-section of the heating rod, said coupling piece being connected with an end of the heating rod by a pin in such a manner that when the corresponding terminal is axially pulled out of the furnace said heating rod is also withdrawn, and the other end of the heating rod being connected to a cooled terminal by means of a coupling piece having a steeply conical bore engaging a correspondingly conical end portion of the rod.

8. An electric furnace comprising a `resistance heating rod, a water-cooled metal terminal connected to said rod at one end of the latter, a carriage disposed outside the furnace, current feed wires connected to said carriage, means on said carriage for detachably clamping said terminal in the carriage, a stationary support in which said carriage is mounted with capacity for limited movement relatively to the furnace in a direction axial to the heating rod, a coupling piece int-erposed between the resistance heating rod and the terminal, said piece consisting of a material possessing similar properties to the heating rod and its diameter corresponding approximately to that of the terminal and itscross-section faces and its faces of contact with the rod and terminal being of greater dimensions than the cross-section of the heating rod, said coupling piece being connected with an end of the heating rod by a pin in such a manner that when the corresponding terminal is axially pulled out of the furnace said heating rod is also withdrawn, and the coupling piece being in the form of a sleeve having two oppositely directed cavities of similar dimension onefor the terminal and the other for the end of the heating rod.

OTTO J UNKER. ERICH BREUER. KARL KNAUFF. 

